Mobile communications systems are made up of a plurality of cells. Each cell provides a radio communications center through which a mobile station establishes a call or other communications session with another mobile station or a terminal connected to either a circuit-switched network (e.g., public-switched telephone network or PSTN) or a packet-switched data network. Each cell includes a radio base station, with each base station coupled to a switching center that controls processing of calls or other communications sessions between or among mobile stations or between mobile stations and terminals connected to a circuit-switched or a packet-switched network.
Various wireless protocols exist for defining communications in a wireless network. One type of protocol is based on the time-division multiple access (TDMA) technology, such as the TIA/EIA-136 standard provided by the Telecommunications Industry Association (TIA) or the Global System for Mobile (GSM) standard. Another type of protocol for wireless communications is based on the code-division multiple access (CDMA) technology. CDMA is a spread spectrum wireless communications protocol in which transmission is based on the spread spectrum modulation technique to allow many users to have access to the same band of carriers.
Traditionally, wireless networks have been designed for carrying circuit-switched voice traffic. However, with the wide availability of the Internet and intranets, packet-switched communications (e.g., web browsing, electronic mail, instant messaging, electronic gaming, and so forth) have become common. As a result, third generation (3G) and beyond wireless technologies are being developed and implemented to provide higher bandwidth and more efficient packet-switched communications (of data as well as voice and other forms of real-time data) over wireless networks.
In the CDMA context, a CDMA 2000 family of standards has been developed that is capable of supporting both traditional circuit-switched wireless communications protocols have also been developed. On the TDMA side, packet-switched wireless communications protocols have also been developed.
The first phase of CDMA 2000 is referred to as 1xRTT (also referred to as 3G1X or 1X), which is designed to increase voice capacity as well as to support data transmission speeds that are faster than typically available. In addition, for even higher data rates, a High Rate Packet Data (HRPD) wireless technology has been developed. HRPD is defined as TIA/EIA/IS-856, “CDMA 2000, High Rate Packet Data Air Interface Specification,” which is adopted by the TIA. The HRPD technology is also referred to as the 1xEV-DO or 1xEV technology. 1xEV-DO provides relatively high data transfer rates over the air interface between mobile stations and base stations.
To establish 1xEV-DO session over a wireless link, various session configuration messages are exchanged over a radio connection between the mobile station and the radio network controller over traffic channels. However, other types of messages for establishing the 1xEV-DO session are exchanged on control channels, such as location update messages and hardware identifier messages. Typically, exchanging messages over a control channel usually takes longer than exchanging messages over traffic channels when establishing a 1xEV-DO session.
The 1xEV-DO session establishment is not complete until the location update messages and hardware identifier messages have been exchanged. However, if the mobile station is located near a boundary between two radio network controllers, handoff may occur from one radio network controller to another radio network controller. As a result of a handoff procedure, the radio connection may be closed prior to all messages needed for 1xEV-DO session establishment being exchanged. Closing the radio connection prior to complete session establishment results in 1xEV-DO session establishment failure, since all messages needed for session establishment has not yet been exchanged. After handoff, the mobile station will have to repeat the procedures for establishing the 1xEV-DO session with the new radio network controller. Having to repeat such procedures is time-consuming and wastes radio resources of the wireless communications network.